A conventional silicon wafer is manufactured through a single crystal growth process, a slicing process, a grinding process, a lapping process, a polishing process, and a cleaning process to remove abrasive or foreign substances adhering to a wafer after the polishing process.
A wafer produced by such a method is referred to as a polished wafer, and a wafer in which another monocrystalline film (epitaxial layer) is grown on a surface of a polished wafer is referred to as to an epitaxial wafer.
The epitaxial wafer has fewer defects than the polished wafer and has characteristics of controlling a concentration and kind of impurities. In addition, the epitaxial layer has high purity and excellent crystallinity, which is advantageous for improving an yield and device properties of a highly integrated semiconductor device. Chemical vapor deposition is a process of growing a thin layer of material on a target, such as a semiconductor wafer, whereby a layer having a different conductivity may be deposited on the wafer to produce desired electrical properties.
A chemical vapor deposition apparatus for depositing an epitaxial layer on a wafer surface is configured to include a process chamber in which an epitaxial layer is deposited, a susceptor mounted in the chamber, a heating lamp provided in upper and lower portions of the process chamber, and a gas injection unit for injecting a source gas onto a wafer. The source gas injected from the gas injection unit forms an epitaxial layer on a wafer placed on the susceptor.
A chamber of an epi reactor for growing an epitaxial layer on a wafer includes a lot of moisture including metal impurities generated when an epitaxial process is performed at a high temperature. When such impurities are present inside the chamber, it is impossible to manufacture a high-quality epitaxial wafer, and thus, after a manufacturing process of an epitaxial wafer is completed, it is necessary to remove impurities remaining inside the chamber and form an atmosphere in which an epitaxial process of a next batch may be performed.
That is, after various processes are performed inside the chamber, a preventive maintenance (PM) is executed. Accordingly, residual moisture and metal impurities are generated inside the chamber after the PM. Thus, a process of preparing for a restart of a growth apparatus is performed so that an epitaxial wafer may be manufactured.
When a restart procedure of an epitaxial growth system is performed, a process recipe is provided for removing moisture and various contamination sources remaining in a thermally stabilized state in the epitaxial reactor, and steps of heating and stabilizing inside the chamber for a sufficient time to secure the quality of the wafer are repeated to perform the restart procedure.
However, since productivity of an epitaxial wafer decreases as the time for performing a restart procedure takes longer, it is necessary to find out a method capable of improving the productivity of an epitaxial wafer by reducing the time required for a restart procedure of an epitaxial reactor.